https://adventofcode.com/2018

4.js

var formatDate = d=>`${d.getFullYear()}-${`${d.getMonth()+1}`.padStart(2,0)}-${`${d.getDate()}`.padStart(2,0)}`
var es=document.body.textContent.trim().split('\n').map(l => {let [,d,s]=l.split(/\[|\] /g); return {d: new Date(d), s}}).sort((a,b)=>a.d-b.d)
var xs=es.map(({d,s}) => { let m=d.getMinutes(); if (d.getHours()===23){d.setDate(d.getDate()+1);m=0;} return {date: formatDate(d), m,d,s}} )
var days=xs.reduce((o,{date,m,s})=>{const slots=o[date]&&o[date].slots||Array.from({length:60},()=>0); let g=s.match(/#\d+/); if (s.startsWith('falls')){for(let i=m;i<slots.length;i++)slots[i]=1} if (s.startsWith('wakes')){for(let i=m;i<slots.length;i++)slots[i]=0} return {...o,[date]:{...o[date],slots,...g&&{guard:g[0]}}} }, {})
var guards=Object.values(days).reduce((o, {slots,guard}) => {let name=guard.slice(1); const sleeptime=o[name]||0; return {...o,[name]:sleeptime+slots.reduce((a,b)=>a+b)};}, {})
var ds = Object.entries(days).filter(([date, o]) => o.guard==='#2593').map(([date, {slots}]) => slots)
Math.max(...ds.reduce((acc, slots) => acc.map((x,i)=>x+slots[i]), Array.from({length:60},()=>0)))
ds.reduce((acc, slots) => acc.map((x,i)=>x+slots[i]), Array.from({length:60},()=>0)).indexOf(14)
2593*40

var gs=Object.values(days).reduce((o, {slots,guard}) => {let name=guard.slice(1); const sl=o[name]||Array.from({length:60},()=>0); return {...o,[name]:sl.map((x,i)=>x+slots[i])};}, {})
Object.entries(gs).map(([id, vs]) => [id, Math.max(...vs)])
Object.entries(gs).map(([id, vs]) => [id, vs.indexOf(Math.max(...vs))])
3361*33